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Two French laboratories have successfully vaccinated and
protected mice by feeding them starch derived from green algae and
genetically modified to carry vaccine proteins.

Researchers from the Centre d'Infection et d'Immunité de Lille
(CNRS/Inserm/Institut Pasteur de Lille/Universités Lille 1 et 2) and
the Unité de Glycobiologie Structurale et Fonctionnelle (CNRS/Université
Lille 1) have developed a new vaccine strategy based on the
technique, which they have patented.

They used antigens that have shown their efficacy in
'conventional' vaccinations as vaccine candidates. They fused these
antigens to an enzyme (GBSS) in a starch granule from the green
algae, Chlamydomonas reinhardtii. This enzyme has the
particularity of functioning inside the starch granule and of being
protected, along with the antigens grafted to it, against
degradation by other enzymes.

In this way, the researchers were able to produce several murine
and human antigens of Plasmodium within starch grains.
These grains were then ingested by mice inoculated with the
parasite. The researchers demonstrated that the mice were vaccinated
by the starch grains, which significantly protected them against
infection.

Starch is the insoluble and semi-crystalline polysaccharide (2)
that is the most commonly found in photosynthetic organisms. A
starch grain can easily be produced from a plant extract and
purified in large quantities. It has a very stable structure and can
be stored for months with no particular precaution, even if it
undergoes temperature variations. It is easily assimilated through
digestion and has a major ecological and financial interest, with
very low production costs.

The starch of edible plants could be transformed in the same way
as that of the algae Chlamydomonas reinhardtii. Researchers
are thus looking at the possibility of using starch from
multi-cellular algae used in Africa as a food supplement, but also
from maize and potatoes.

Administered to children under three years of age, who are at
high-risk of malaria-related mortality, such plants could be both a
food source and a vaccine. This strategy would allow simple
vaccination, avoid storage problems and syringes, and thus eliminate
potential HIV contamination.

The researchers now plan to test the efficacy of various
Plasmodium antigens and determine whether such strategy can be
applied to humans by verifying it has no side effects.

According to the WHO, malaria affects approximately 300 to 500
million people worldwide and kills one million each year, mostly
young children. Insecticide-resistant mosquitoes carrying the
disease and multi-drug-resistant parasites are on the increase.

In this context, the development of a vaccine that alleviates
symptoms and reduces mortality would be a valuable new tool in the
fight against malaria. Researchers aim to test the efficacy of
vaccine candidates among proteins that allow the parasite to
penetrate host cells and infect them, in order to devise the best
strategy for vaccine delivery.